The invention relates to a method and composition for sealing well bores and, more particularly, for sealing the annular space between a bore hole and a casing positioned in the bore hole.
During the completion of a subterranean well, especially a hydrocarbon producing or injection well, a casing is positioned within the well after drilling so as to provide a conduit through which fluids can be transported. Conventionally, the casing is cemented in place by positioning a cement material in the annular space to provide an annular seal between the casing and the geological strata through which the bore has been drilled to support the bore and the casing.
Conventional cement materials used for such sealing suffer from loss of integrity due to chemical attack, high temperature and/or fluids encountered in the well environment. Further, cement slurry is subject to incomplete seal with the bore hole and casing, and can frequently allow fluid migration or channeling which interferes with the effective seal which is needed. In addition, high curing time is required.
Further, once the cement has fully set, it is a substantially rigid structure, and is susceptible to damage should the environment in which it positioned experience any shifting and the like.
It is clear that the need remains for an improved method and composition for sealing well bores.
It is therefore the primary object of the present invention to provide a method and composition for sealing well bores and annular spaces within such wells which avoids the above problems.
It is a further object of the present invention to provide such a method and composition which does not result in substantially increased cost.
It is still another object of the present invention to provide such a method and composition which can be disposed in conventional wells using conventional equipment.
Other objects and advantages of the present invention will appear herein below.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According to the invention, a method is provided for sealing an annular space between a bore hole and a casing, which method comprises the steps of providing a fluid sealing system comprising a particulate material and a bonding agent; positioning the fluid sealing system in the annular space whereby the particulate material adheres to walls of the bore hole and the casing; and curing the fluid sealing system so as to form a solid seal in the annular space.
According to the invention, a composition is also provided for use in sealing bore holes and annular spaces, which composition comprises a fluid sealing system containing a particulate material and a bonding agent, wherein said bonding agent is activatable to bond particles of said particulate material and form a solid seal.
The composition and method in accordance with the present invention provide a system which adheres to walls of the well bore and casing and thereby provides greater integrity of the seal, with significantly reduced chance for fluid migration, channeling and the like. Further, the method and composition of the present invention provide a more flexible final structure, which is less susceptible to damage due to geographical shifting and the like, and the composition can be provided at comparable cost to conventional cement.